1. Field of the Invention
The present invention relates to an optical telecommunications network and to switching structures suitable for use in such a network.
2. Related Art
Optical transmission systems potentially offer a basis for telecommunications networks of very high capacity. It is envisaged that this capacity will be used to provide connections for large numbers of systems to high bandwidth services such as high bit rate data communications, video on demand VoD or video telephony. However, in practice when it comes to realising such a high capacity network, the design of appropriate switching technologies is found to be a major constraint on the performance of the network. With current technologies, the switching structures are electronic (e.g. ATM switches) and are therefore limited to capacities considerably lower than those which can be achieved in the optical domain. Control and management of the switching function also provides further difficulties and there is a need to minimise software costs for call processing, network intelligence, network management and service management.
In order to minimise the use of active switches and the associated constraints discussed above, it has been proposed to use passive optical networks PONs. However hitherto, such PONs have been used for multiplexing and consolidation of access traffic to a local switch node with customer to customer connections still being provided by switching centrally at the nodes.